The water content of the stratum corneum decreases as the skin becomes more rough, dry, or aged. To obtain a pleasant feel for the skin, or to obtain an attractive outerlayer of the skin, various moisture retaining agents or oils are often incorporated into cosmetic compositions. Oils tend to increase the water content of the stratum corneum by occlusion of the skin surface thereby softening the stratum corneum. On the other hand, aqueous moisture retaining agents tend to increase the water content of the stratum corneum because of their water retaining ability, also resulting in a softening of the stratum corneum. This is why cosmetic compositions containing various oils or aqueous moisture retaining agents, improve the feel of the skin and the skin's appearance. However, oils have the problem that they tend to be greasy or cause a skin shine. Aqueous moisture retaining agents are likely to be washed away with water, resulting in a short-lived cosmetic effect.
Intercellular lipids, are found in the intercellular portions of the stratum corneum, and form stratified structures which aid in the adhesion of the stratum corneum cells, and in the hydration of the stratum corneum. Such lipids, extracted from the skin have been used in cosmetic compositions instead of oils or aqueous moisturizing agents, (Japanese Laid Open Patent Application Nos. 62-29508/1987, 62-120308/1987). Likewise synthetic compounds having analogous structures to intercellular lipids have also been used for similar purposes (Japanese Laid Open Application No. 62-228048/1987, and U.S. Pat. No. 4,778,823).
Amphiphatic lipids, such as the intercellular lipids, are solid at room temperature (25.degree. C.) and when used in cosmetics are incorporated in admixture with the oils and/or emulsifying agents, or are dissolved in large amounts of surfactant.
Opaque, white emulsions are obtained simply by mixing the lipids with the oils and/or emulsifiers, although it is difficult to incorporate intercellular lipids stably into cosmetic compositions wherein the lipids are in high concentration.
Transparent cosmetics are obtained by the use of a large amount of surfactant and lipids. Unfortunately large amounts of surfactant, tends to interfere with the function of the amphiphatic lipids, sometimes resulting in skin irritation due to the surfactants.
It would be desirable, therefore, to provide a cosmetic composition which does not irritate the skin, but which contains the amphiphatic lipids in a stable and clear transparent or semi-transparent condition.